selinux: declare path parameters of _genfs_sid const

The path parameter is only read from in security_genfs_sid(),
selinux_policy_genfs_sid() and __security_genfs_sid(). Since a string
literal is passed as argument, declare the parameter const.
Also align the parameter names in the declaration and definition.

Reported by clang [-Wwrite-strings]:

    security/selinux/hooks.c:553:60: error: passing 'const char [2]'
      to parameter of type 'char *' discards qualifiers
      [-Wincompatible-pointer-types-discards-qualifiers]
            rc = security_genfs_sid(&selinux_state, ... , /,
                                                          ^~~
    ./security/selinux/include/security.h:389:36: note: passing
      argument to parameter 'name' here
                           const char *fstype, char *name, u16 sclass,
                                                     ^
Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
[PM: wrapped description]
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/include/security.h

@@ -386,11 +386,11 @@ int security_get_allow_unknown(struct selinux_state *state);
 int security_fs_use(struct selinux_state *state, struct super_block *sb);
 
 int security_genfs_sid(struct selinux_state *state,
-		       const char *fstype, char *name, u16 sclass,
+		       const char *fstype, const char *path, u16 sclass,
 		       u32 *sid);
 
 int selinux_policy_genfs_sid(struct selinux_policy *policy,
-		       const char *fstype, char *name, u16 sclass,
+		       const char *fstype, const char *path, u16 sclass,
 		       u32 *sid);
 
 #ifdef CONFIG_NETLABEL

security/selinux/ss/services.c

@@ -2875,7 +2875,7 @@ int security_get_user_sids(struct selinux_state *state,
  */
 static inline int __security_genfs_sid(struct selinux_policy *policy,
 				       const char *fstype,
-				       char *path,
+				       const char *path,
 				       u16 orig_sclass,
 				       u32 *sid)
 {
@@ -2928,7 +2928,7 @@ static inline int __security_genfs_sid(struct selinux_policy *policy,
  */
 int security_genfs_sid(struct selinux_state *state,
 		       const char *fstype,
-		       char *path,
+		       const char *path,
 		       u16 orig_sclass,
 		       u32 *sid)
 {
@@ -2952,7 +2952,7 @@ int security_genfs_sid(struct selinux_state *state,
 
 int selinux_policy_genfs_sid(struct selinux_policy *policy,
 			const char *fstype,
-			char *path,
+			const char *path,
 			u16 orig_sclass,
 			u32 *sid)
 {